Hand powered drills were used exclusively in the days before
electricity. You have complete control over the speed, torque and
pressure, and you can do all your stone setting with them.
You cannot shave edges or do carving with burrs in an eggbeater; for
that you need some gravers for fine work; and some small chisels and
a hammer for heavy carving.
My mentor used an achcimedes drill (like a pump drill with ropes),
but I preferred the eggbeater drill for jewellery. The eggbeater
needs to turn freely; if there is any stiffness then the sideways
forces while turning will break the small drill bits.
Electricity is not essential, but it does make things quicker and
perhaps a little easier.